The present invention relates to a sanding head providing for the extraction of the dust produced during sanding, including a shaft casing, a shaft rotatably mounted in the casing and capable of being driven by motor means, a circular backing plate of a ventilated type which is connected to one end of the shaft, said circular backing plate being provided in its front face with ventilating grooves and having in its center a hollow cylindrical element which has a closed front end and which is provided, adjacent its closed front end, with lateral windows communicating the inside of the hollow cylindrical element with the ventilating grooves, and means for detachably fixing an abrasive disk to the closed front end of the hollow cylindrical element.
Applicant's U.S. patent application Ser. No. 835,699 filed on Sept., 22, 1977, already discloses a sanding apparatus comprising a sanding head of the above described type. In the sanding apparatus described in said U.S. patent application, the extraction of dust caused by the abrasive paper disk takes place through the drive shaft of the backing plate, which is formed as a hollow shaft. The rotation of the hollow shaft is obtained by means of two bevel gears which are fixed respectively to the hollow shaft and to the shaft of the motor of the sanding apparatus, as in conventional sanding apparatus in which the output shaft, to which the circular backing plate is fixed, extends perpendicularly to the longitudinal axis of the body of the sanding apparatus which contains the drive motor. In the above mentioned U.S. patent application, it is also contemplated to adapt the casing of the sanding head to a motor unit, e.g. the motor unit of a drilling apparatus, for instance on electric drill, capable of receiving different accessories. However, whereas the use of two shafts at right angles and two bevel gears fixed respectively on said shafts is rational in the case of a sanding apparatus in which these elements already exist and are disposed in the same way, such an arrangement is less rational in the case of a sanding head adaptable to the motor unit of an electric drill able to receive different accessories. In fact, the use of two shafts at right angles, one of which is hollow, and two bevel gears, complicates the construction of the sanding head and increases its cost price.